Ambulatory blood pressure monitoring

INTRODUCTION

Ambulatory blood pressure monitoring (ABPM) is becoming increasingly recommended for routine clinical practice. It may be particularly useful in evaluating the patient with variable blood pressure readings in the office or in a patient with wide discrepancies between the blood pressure readings at home and at the clinician’s office (ie, “white coat” hypertension).

MEASUREMENT OF ABPM

Ambulatory blood pressure monitoring (ABPM) is determined using a device worn by the patient that takes blood pressure measurements over a 24-hour period, usually every 30 minutes during the daytime and every 30 to 60 minutes during sleep. These blood pressures are recorded on the device, and the average day (diurnal) or night (nocturnal) blood pressures are determined from the data by a computer. The percentage of blood pressure readings exceeding the upper limit of normal can also be calculated.

INDICATIONS FOR ABPM

In accordance with published practice guidelines and expert panel recommendations, ambulatory blood pressure monitoring (ABPM) can be used in the following circumstances:

●White coat hypertension

●Suspected episodic hypertension (eg, pheochromocytoma)

●Resistant hypertension

●Symptoms of very low blood pressure while taking antihypertensive medications

●Autonomic dysfunction

Some expert panels, including the United States Preventive Services Task Force (USPSTF) recommend that ABPM should also be used to confirm a new diagnosis of hypertension in outpatients who have elevated office blood pressure. There are a number of other potential indications advocated by some experts, which include:

●Are they nondippers ? (people who’s blood pressure does not drop at night as per normal) or nocturnal hypertension (people with high blood pressure at night)?

●To assess blood pressure during pregnancy when preeclamsia is suspected.

INTERPRETATION OF ABPM

●Twenty-four-hour average blood pressure –Normal blood pressure (BP) is defined as an average blood pressure less than 130/80 mmHg, and hypertension is defined as a blood pressure greater than or equal to 135/85 mmHg.

●Daytime (awake) blood pressure –Normal BP is defined as a blood pressure less than 135/85 mmHg, and hypertension is defined as a blood pressure greater than or equal to 140/90 mmHg. (Lower in diabetics)

●Nighttime (asleep) blood pressure –Normal BP is defined as a blood pressure less than 120/70 mmHg, and hypertension is defined as a blood pressure greater than or equal to 125/75 mmHg.

Dipping blood pressure

The average nocturnal BP is approximately 15 percent lower than daytime values in both normotensive and hypertensive patients. Failure of the blood pressure to fall by at least 10 percent during sleep is called non-dipping.

Masked hypertension

As many as 10 to 40 percent of patients who have normal pressure in the office are hypertensive by ABPM. This phenomenon is called masked hypertension or isolated ambulatory hypertension. Masked hypertension has been associated with an increased long-term risk of chronic hypertension and cardiovascular morbidity. Because of the risk associated with masked hypertension, ABPM should be considered in patients referred for possible hypertension despite repeatedly normal blood pressure when measured in the clinic.

Nocturnal blood pressure and non-dippers

Independent of the degree of hypertension, non-dipping is a risk factor for the development of LVH(left ventricular Hypertrophy), heart failure, and other cardiovascular complications. However, “extreme dipping” (eg, >20 percent nocturnal decline in blood pressure) and a large morning increase in blood pressure are also potentially harmful.

Non-dipping has also been associated with moderately increased albuminuria (formerly called “microalbuminuria”) and more rapid progression of nephropathy(kidney disease) in patients with diabetes mellitus. More importantly, non-dipping may be a risk factor for decline in glomerular filtration rate, and death among patients with chronic kidney disease. The presence of sleep apnea should also be evaluated in non-dippers.

WHITE COAT HYPERTENSION

Many patients are anxious when visiting the doctor, leading to an office blood pressure that may be substantially higher than blood pressure during normal daily activities. The diagnosis of white coat hypertension (also called isolated clinic or office hypertension) is applied to patients with office readings that average more than 140/90 mmHg and reliable out-of-office readings that average less than 140/90 mmHg.

It has been recommended that a patient with mild to moderate elevation in blood pressure should not be diagnosed with hypertension unless the blood pressure remains elevated after three to six visits, unless there is evidence of ongoing end-organ damage.

A white coat hypertension effect may also occur in patients with apparently resistant hypertension. As an example, in one study of nearly 500 treated hypertensive patients (over 60 percent on three or more antihypertensive agents), 37 percent had normal blood pressure on ambulatory blood pressure monitoring (ABPM).

Effect of ABPM on treatment of hypertension

Treatment decisions can be made/changed according to the ambulatory blood pressure findings. When used for the above appropriate indications, one report found that antihypertensive therapy was changed in nearly 50% of the patients, and office blood pressure control was improved in most patients within three months of ambulatory blood pressure monitoring (ABPM).

Ambulatory or self-recorded home readings may detect the early morning blood pressure surge that may contribute to the increased incidence of sudden death, myocardial infarction, and stroke in the early morning hours.

ABPM may help to determine the best timing of administration of antihypertensive agents for non-dippers and those with night-time hypertension. In one study, valsartan taken before bedtime reestablished the night-time reduction in blood pressure.

The effect of repeated ABPM on the treatment of hypertension was assessed in a randomized trial from Belgium in which 419 patients with untreated diastolic hypertension (average ≥95 mmHg) had their subsequent antihypertensive therapy determined by conventional office blood pressure or ABPM at one, two, four, and six months. The mean reduction in blood pressure in the two groups was the same at the end of the study, averaging about 14/10 mmHg. The following significant benefits were noted with the use of ABPM:

The cost of ambulatory blood pressure monitoring (ABPM) is mainly the initial investment in purchasing the monitors and computer software. The average cost (in American dollars) in 2011 for equipment was $2500 to $5000 for each monitor and $2000 to $3000 for the computer software. The monitors are relatively simple to use, and additional costs in training personnel are relatively small. Clinician charges to patients for the use of this modality ranged widely.

However, the money saved by not prescribing antihypertensive medications to patients with white coat hypertension may more than offset the cost of monitoring.

SUMMARY AND RECOMMENDATIONS

● Ambulatory blood pressure monitoring (ABPM) may facilitate achieving blood pressure control and reduce unnecessary treatment. Thus, ABPM can be used in the following situations.

•Suspected white coat hypertension

•Suspected episodic hypertension

•Hypertension resistant to increasing medication

•Hypotensive symptoms while taking antihypertensive medications

●The diagnosis of hypertension based upon ABPM depends upon the time span over which it is interpreted.

•A 24-hour average above 135/85 mmHg

•Daytime (awake) average above 140/90 mmHg

•Nighttime (asleep) average above 125/75 mmHg

●Cardiovascular complications correlate more closely with 24-hour or daytime ABPM than with the office blood pressure.

●White coat hypertension may be associated with an increased risk of stroke, possibly related to later development of chronic hypertension. The risk of cardiovascular complications associated with masked hypertension is similar to that seen with persistent hypertension.

●Failure of the blood pressure to fall by at least 10 percent during sleep (non-dipping) may also be associated with increased cardiovascular risk.

●Self-recorded home blood pressure measurements are an excellent alternative if ABPM is not available or if cost is a concern. Home blood pressure monitoring may also improve hypertension control.

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Ambulatory blood pressure monitoring

INTRODUCTION

Ambulatory blood pressure monitoring (ABPM) is becoming increasingly recommended for routine clinical practice. It may be particularly useful in evaluating the patient with variable blood pressure readings in the office or in a patient with wide discrepancies between the blood pressure readings at home and at the clinician’s office (ie, “white coat” hypertension).

MEASUREMENT OF ABPM

Ambulatory blood pressure monitoring (ABPM) is determined using a device worn by the patient that takes blood pressure measurements over a 24-hour period, usually every 30 minutes during the daytime and every 30 to 60 minutes during sleep. These blood pressures are recorded on the device, and the average day (diurnal) or night (nocturnal) blood pressures are determined from the data by a computer. The percentage of blood pressure readings exceeding the upper limit of normal can also be calculated.

INDICATIONS FOR ABPM

In accordance with published practice guidelines and expert panel recommendations, ambulatory blood pressure monitoring (ABPM) can be used in the following circumstances:

●White coat hypertension

●Suspected episodic hypertension (eg, pheochromocytoma)

●Resistant hypertension

●Symptoms of very low blood pressure while taking antihypertensive medications

●Autonomic dysfunction

Some expert panels, including the United States Preventive Services Task Force (USPSTF) recommend that ABPM should also be used to confirm a new diagnosis of hypertension in outpatients who have elevated office blood pressure. There are a number of other potential indications advocated by some experts, which include:

●Are they nondippers ? (people who’s blood pressure does not drop at night as per normal) or nocturnal hypertension (people with high blood pressure at night)?

●To assess blood pressure during pregnancy when preeclamsia is suspected.

INTERPRETATION OF ABPM

●Twenty-four-hour average blood pressure –Normal blood pressure (BP) is defined as an average blood pressure less than 130/80 mmHg, and hypertension is defined as a blood pressure greater than or equal to 135/85 mmHg.

●Daytime (awake) blood pressure –Normal BP is defined as a blood pressure less than 135/85 mmHg, and hypertension is defined as a blood pressure greater than or equal to 140/90 mmHg. (Lower in diabetics)

●Nighttime (asleep) blood pressure –Normal BP is defined as a blood pressure less than 120/70 mmHg, and hypertension is defined as a blood pressure greater than or equal to 125/75 mmHg.

Dipping blood pressure

The average nocturnal BP is approximately 15 percent lower than daytime values in both normotensive and hypertensive patients. Failure of the blood pressure to fall by at least 10 percent during sleep is called non-dipping.

Masked hypertension

As many as 10 to 40 percent of patients who have normal pressure in the office are hypertensive by ABPM. This phenomenon is called masked hypertension or isolated ambulatory hypertension. Masked hypertension has been associated with an increased long-term risk of chronic hypertension and cardiovascular morbidity. Because of the risk associated with masked hypertension, ABPM should be considered in patients referred for possible hypertension despite repeatedly normal blood pressure when measured in the clinic.

Nocturnal blood pressure and non-dippers

Independent of the degree of hypertension, non-dipping is a risk factor for the development of LVH(left ventricular Hypertrophy), heart failure, and other cardiovascular complications. However, “extreme dipping” (eg, >20 percent nocturnal decline in blood pressure) and a large morning increase in blood pressure are also potentially harmful.

Non-dipping has also been associated with moderately increased albuminuria (formerly called “microalbuminuria”) and more rapid progression of nephropathy(kidney disease) in patients with diabetes mellitus. More importantly, non-dipping may be a risk factor for decline in glomerular filtration rate, and death among patients with chronic kidney disease. The presence of sleep apnea should also be evaluated in non-dippers.

Many patients are anxious when visiting the doctor, leading to an office blood pressure that may be substantially higher than blood pressure during normal daily activities. The diagnosis of white coat hypertension (also called isolated clinic or office hypertension) is applied to patients with office readings that average more than 140/90 mmHg and reliable out-of-office readings that average less than 140/90 mmHg.

It has been recommended that a patient with mild to moderate elevation in blood pressure should not be diagnosed with hypertension unless the blood pressure remains elevated after three to six visits, unless there is evidence of ongoing end-organ damage.

A white coat hypertension effect may also occur in patients with apparently resistant hypertension. As an example, in one study of nearly 500 treated hypertensive patients (over 60 percent on three or more antihypertensive agents), 37 percent had normal blood pressure on ambulatory blood pressure monitoring (ABPM).

Effect of ABPM on treatment of hypertension

Treatment decisions can be made/changed according to the ambulatory blood pressure findings. When used for the above appropriate indications, one report found that antihypertensive therapy was changed in nearly 50% of the patients, and office blood pressure control was improved in most patients within three months of ambulatory blood pressure monitoring (ABPM).

Ambulatory or self-recorded home readings may detect the early morning blood pressure surge that may contribute to the increased incidence of sudden death, myocardial infarction, and stroke in the early morning hours.

ABPM may help to determine the best timing of administration of antihypertensive agents for non-dippers and those with night-time hypertension. In one study, valsartan taken before bedtime reestablished the night-time reduction in blood pressure.

The effect of repeated ABPM on the treatment of hypertension was assessed in a randomized trial from Belgium in which 419 patients with untreated diastolic hypertension (average ≥95 mmHg) had their subsequent antihypertensive therapy determined by conventional office blood pressure or ABPM at one, two, four, and six months. The mean reduction in blood pressure in the two groups was the same at the end of the study, averaging about 14/10 mmHg. The following significant benefits were noted with the use of ABPM:

The cost of ambulatory blood pressure monitoring (ABPM) is mainly the initial investment in purchasing the monitors and computer software. The average cost (in American dollars) in 2011 for equipment was $2500 to $5000 for each monitor and $2000 to $3000 for the computer software. The monitors are relatively simple to use, and additional costs in training personnel are relatively small. Clinician charges to patients for the use of this modality ranged widely.

However, the money saved by not prescribing antihypertensive medications to patients with white coat hypertension may more than offset the cost of monitoring.

SUMMARY AND RECOMMENDATIONS

● Ambulatory blood pressure monitoring (ABPM) may facilitate achieving blood pressure control and reduce unnecessary treatment. Thus, ABPM can be used in the following situations.

•Suspected white coat hypertension

•Suspected episodic hypertension

•Hypertension resistant to increasing medication

•Hypotensive symptoms while taking antihypertensive medications

●The diagnosis of hypertension based upon ABPM depends upon the time span over which it is interpreted.

•A 24-hour average above 135/85 mmHg

•Daytime (awake) average above 140/90 mmHg

•Nighttime (asleep) average above 125/75 mmHg

●Cardiovascular complications correlate more closely with 24-hour or daytime ABPM than with the office blood pressure.

●White coat hypertension may be associated with an increased risk of stroke, possibly related to later development of chronic hypertension. The risk of cardiovascular complications associated with masked hypertension is similar to that seen with persistent hypertension.

●Failure of the blood pressure to fall by at least 10 percent during sleep (non-dipping) may also be associated with increased cardiovascular risk.

●Self-recorded home blood pressure measurements are an excellent alternative if ABPM is not available or if cost is a concern. Home blood pressure monitoring may also improve hypertension control.